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The PVD-vacuum preloading method combined with airbags is a new soft ground treatment technology that can provide additional consolidation pressure and reduce lateral deformation towards the improvement area caused by traditional PVD-vacuum preloading. However, continuous airbag pressurization tends to create large cavities in the soil, and the optimal timing for airbag loading is also unclear. To address the aforementioned issues, this paper proposes an intermittent airbag pressurization method, adding small-diameter airbags between adjacent PVDs and intermittently inflating the airbags. Through indoor model test, the water discharge characteristics, improvement effect, improvement mechanism, and foundation settlement characteristics under intermittent airbag pressure were studied, proving that intermittent airbag pressure can significantly reduce early soil rebound. A calculation method for the airbag expansion diameter was proposed, and its feasibility was verified through experimental results. Finally, the optimal time period for intermittent airbag loading was clarified. [Display omitted] • Proposing airbag loading method for airbag vacuum preloading. • Water discharge and settlement characteristics under intermittent airbag pressure and vacuum pressure were studied. • Proposing a calculation method for the expansion diameter of the airbag. • A settlement prediction method for airbag vacuum preloading was proposed. • The optimal time period for intermittent airbag loading was clarified. [ABSTRACT FROM AUTHOR]

AbstractTo investigate the impact of traffic loading on the deformation characteristics of soft dredger fill, a series of dynamic triaxial tests of soft dredger fill were carried out. The deformation characteristics of the soft dredger fill under varying confining pressures and dynamic stress ratios were analyzed comparatively. The test results indicate that the cumulative plastic strain curve of the soft dredger fill exhibits three distinct patterns: destructive, critical, and stable; Based on the cumulative plastic strain development law of the dredger fill, an empirical formula of critical dynamic stress and the prediction model of cumulative plastic strain development were established, considering the influence of confining pressure. Under continuous loading, the hysteresis curve of soft dredger fill showed pronounced non-linearity, and hysteresis. Initially, the curve exhibited an “ellipse” shape, transitioning to a “crescent” shape in the middle and late stages. The higher the dynamic stress ratio, the greater the height and width of the hysteresis loop. These findings provide valuable insights into the dynamic behavior of dredger fill under traffic loading. [ABSTRACT FROM AUTHOR]

China's lowland rural rivers are facing severe eutrophication problems due to excessive phosphorus (P) from anthropogenic activities. However, quantifying P dynamics in a lowland rural river is challenging due to its complex interaction with surrounding areas. A P dynamic model (River-P) was specifically designed for lowland rural rivers to address this challenge. This model was coupled with the Environmental Fluid Dynamics Code (EFDC) and the Phosphorus Dynamic Model for lowland Polder systems (PDP) to characterize P dynamics under the impact of dredging in a lowland rural river. Based on a two-year (2020–2021) dataset from a representative lowland rural river in the Lake Taihu Basin, China, the coupled model was calibrated and achieved a model performance (R 2>0.59, RMSE<0.04 mg/L) for total P (TP) concentrations. Our research in the study river revealed that (1) the time scale for the effectiveness of sediment dredging for P control was ∼300 days, with an increase in P retention capacity by 74.8 kg/year and a decrease in TP concentrations of 23% after dredging. (2) Dredging significantly reduced P release from sediment by 98%, while increased P resuspension and settling capacities by 16% and 46%, respectively. (3) The sediment-water interface (SWI) plays a critical role in P transfer within the river, as resuspension accounts for 16% of TP imports, and settling accounts for 47% of TP exports. Given the large P retention capacity of lowland rural rivers, drainage ditches and ponds with macrophytes are promising approaches to enhance P retention capacity. Our study provides valuable insights for local environmental departments, allowing a comprehensive understanding of P dynamics in lowland rural rivers. This enable the evaluation of the efficacy of sediment dredging in P control and the implementation of corresponding P control measures. [Display omitted] [ABSTRACT FROM AUTHOR]

Dredged sludge usually has high water content and poor engineering properties, which would be unfavorable for its rapid resource utilization. Meanwhile, straw fiber is an environmentally friendly material for improving the mechanical behavior of soil. In this research, a series of shrinkage tests were conducted to investigate the straw fiber effects on the shrinkage behavior of dredged sludge with high water content. Four initial water contents and straw fiber amounts were designed. The water content and crack development were recorded throughout the test. According to the test results, a reduction in water content regarding drying time can be divided into three stages: the constant-rate stage, the falling-rate stage, and the residual stage. At the falling-rate stage, water evaporation is affected significantly by straw fiber. Compared with the sample without straw fiber, the influence of straw fiber on the water evaporation of dredged sludge depends upon the initial water content and the straw fiber content. The straw fiber shows an overall inhibitory effect on the initiation and development of cracks for the tested samples. Moreover, the influence of straw fiber on the shrinkage behavior of dredged sludge depends upon the initial water content and fiber content. [ABSTRACT FROM AUTHOR]

Vacuum preloading combined with flocculation has shown great potential for improving the dredged sludge's dewatering and consolidation. To identify a suitable flocculant combined with vacuum preloading method, this study investigated the effects of various common flocculants on the sludge's filtration properties and consolidation behaviors. The results indicated that dual-use of polymeric aluminium chloride (PAC) and polyacrylamide (PAM) had the most significant improvement on sludge's filtration performance, as reflected by capillary suction time. In addition, a single dose of PAM had the most substantial improvement on the sludge's compressibility. While, lime improved the sludge's permeability the most. To predict the consolidation settlement of flocculated sludge during vacuum preloading, a method was proposed based on a small homemade vacuum preloading apparatus and the Taylor method. The influence of different flocculants on sludge properties was also analyzed based on their flocculation mechanisms and microstructure. Finally, an appropriate flocculant for the sludge in vacuum preloading projects was suggested in accordance with different project goals. [ABSTRACT FROM AUTHOR]

Clogging in the prefabricated vertical drains (PVDs) and soils is an inherent feature associated with vacuum treatment of slurry ground. The clogging column is characterized by nonlinear growth of volume over time and nonlinear permeability distribution along the radial direction. This study aims to develop a drain-well consolidation model for vacuum treatment of dredged slurry, with specific considerations of the nonlinear behaviors of the clogging column and PVD drainage capacity. The constitutive compression and permeation behaviors of the dredged slurry are described by extended power functions, which avoids the singularities associated with the conventional logarithmic constitutive equations when the effective consolidation stress approaches zero. Parametric studies were conducted to explore the consolidation effects while considering different combinations of parameters that govern the nonlinear behaviors of the clogging column and PVD-drainage capacity. The significance of considering the abovementioned nonlinear behaviors was demonstrated by comparing the field test results on a dredged slurry ground. Results indicate that clogging primarily affects consolidation by causing a nonlinear permeability distribution along the radial direction of the clogging column and nonlinear attenuation of PVD-drainage capacity. [ABSTRACT FROM AUTHOR]

Safe navigation in rivers often requires repeated dredging operations. River dunes are causing shallow areas, so a better understanding of dune behavior can aid decision‐making on dredging strategies. A new dune‐tracking method was developed to analyze dunes after dredging. This knowledge was combined with information on dredging methods and intensity. This enables the analysis of dune development after dredging and the assessment of the impact of dredging methods such as topping (removing sediment from the crest) and swiping (transferring sediment from the crest to the trough). The results show that dredging increases the growth rate of dunes, especially when the discharge increases after dredging. For the studied dredging intensities, topping has a more pronounced effect than swiping on the immediate reduction of dune height. The changes in dune heights due to dredging are within the natural dune height variability. In the long term, topped dunes exhibit larger growth rates than those undergoing swiping. So dredging does have an effect on dune dynamics, in particular on the dune height growth rates. Plain Language Summary: River dunes are bedforms in the river bed that can create shallow areas, which may hinder navigation. To keep the shipping channel deep enough, regular dredging is needed. A new method to track these dunes was developed to examine the impact of two dredging methods on the dune development: topping (removing sediment from the top) and swiping (moving sediment from top to trough). The results show that dredging when water levels are increasing, results in increased dune height growth rates. Dredging when water levels are lowering can result in both increased and decreased growth rates, while in this case the dredging helps the dunes to change to their eventual lower height. Among the dredging methods studied, topping reduces the height of the dunes more than swiping. But in the long run, dunes that have been topped tend to grow back bigger compared to those that have been swiped. Dredging does influence river dune dynamics, but the effect on dune height is similar to variability in dune height that occurs naturally. The study helps us understand better how different dredging methods impact these river dunes, which can help in planning better ways to keep rivers safe and easy to navigate. Key Points: Applying a two‐dimensional wavelet filter on dunes allows for reliable dune tracking with cross‐correlationDredging results in an increased dune height growth rate when the discharge increasesThe dredging method, that is, topping or swiping, matters for the recovery of the dunes [ABSTRACT FROM AUTHOR]

Purpose: Maintenance dredging can often hinder port operations resulting in waiting times for seagoing vessels. The purpose of this paper is to investigate the dynamics between maintenance dredging activities and seagoing vessels, specifically focusing on how waiting times can be reduced. Then, the role of selecting different maintenance dredging strategies in reducing these waiting times is outlined. Methods: The study analyzes historical automatic identification system (AIS) data to identify the interaction between maintenance dredging and seagoing vessels and quantify the hindrance periods for the Mississippihaven case study in the Port of Rotterdam, the Netherlands. The trajectories of the vessels are analyzed in a simple case to show how the vessels interact and how the waiting times are quantified. The interactions are checked with the Port of Rotterdam for different port calls to ensure that maintenance dredging was the reason for these delays. Results: By analyzing the AIS data analysis of vessels in a given time window, the dredgers for maintenance work can be identified and their activities within or near the terminal can be determined. In addition, the waiting time of the seagoing vessel caused by the maintenance dredging is quantified at the terminal entrance. Conclusion: The study discusses how the maintenance dredging operations could be improved by adjusting the loading and sailing phases of maintenance dredging and provides some theoretical and managerial insights. Alternative port maintenance strategies to minimize the waiting time caused by the hindrance are also discussed. [ABSTRACT FROM AUTHOR]

The Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus has suffered population declines throughout its range. Many knowledge gaps exist regarding how to mitigate threats and better inform recovery efforts. This study examined survival of juveniles during their movements through river reaches undergoing channel maintenance dredging operations. During 2019 and 2020, 268 (30-71cm fork length) juvenile Atlantic Sturgeon were captured and released in proximity to an active cutterhead suction dredge at three sites within the James River, Virginia. Juveniles were captured, some presumed feeding, around 95-145m from the dredge in areas that could easily be avoided if the dredge created a stressful environment. No significant trends in catch-per-unit-effort were found when trawl catch was compared to a reference location or when monitoring gill net catch 100m down current of a dredge over a month-long period at one of the sites. Twenty-nine of the 229 gill net captures were implanted with acoustic tags and telemetry was used to track their movements throughout the river. Four telemetered juveniles tagged prior to this project were also detected moving within dredge operations. Cumulatively, tagged juveniles made at least 125 passes of the dredging operations with no evidence of mortality. All tagged juveniles still within the river were detected following the cessation of dredging. The results of this study support that age 1-2yr Atlantic Sturgeon show no avoidance behavior of areas 100m of an active cutterhead suction dredge and move past dredge operations with low-risk of mortality. [ABSTRACT FROM AUTHOR]

A Trailing Suction Hopper Dredger (TSHD) in the sailing process, excavating seabed sediment with the drag head and pumping it through the pipeline to the spoil hopper sedimentation. The spoil hopper sedimentation process, as a critical factor affecting the loading yield and efficiency of a dredger, is susceptible to the influence of different average sand grain diameter d m . However, the soil type tends to change continuously during the loading process, making it difficult to obtain the d m by measurement or calculation. In this paper, combined with the existing simplified one-dimensional sedimentation model and simulated loading data, the Bootstrap Particle Filter (BPF), Gaussian Particle Swarm Optimized Particle Filter (GPSO-PF), Assisted Particle Filter (APF), Continuous-Discrete Feedback Particle Filter based on the constant feedback gain approximation (CD-FPF-CG) and the Galerkin method feedback gain approximation (CD-FPF-GL) are applied in the numerical simulations for online estimation of important variables such as the average sand grain diameter d m , the sand bed height h s and mass m s , respectively. The simulations results show that the CD-FPF-CG has a higher numerical accuracy and efficiency than the BPF, GPSO-PF, APF and CD-FPF-GL. Therefore, the CD-FPF-CG is used to estimate the above important variables for the actual vessel and the initial value of the average sand grain diameter d m for the CD-FPF-CG is determined via Simulated Annealing Multiple Population Genetic Algorithm (SAMPGA). [ABSTRACT FROM AUTHOR]

AbstractMultilayer PHDs combined with vacuum pressure for the treatment of dredged sludge yards are effective in avoiding the bending effect of drainage bodies during consolidation. However, the existing theory of self-weight consolidation cannot reflect the actual consolidation properties of dredged sludge treated with multilayer PHDs combined with vacuum pressure. In this study, the nonlinear large-strain consolidation model of dredged sludge treated with multilayer PHDs combined with vacuum pressure was established, considering the nonlinear compressibility and permeability of dredged sludge, self-weight stress of dredged sludge and the variation of dredged sludge height with time. The reliability of the model is verified by comparison with existing consolidation theory, indoor test, and field test data. By researching the effect of the PHDs laying ratios, the height of each dredged sludge layer, and the stacking process time on the consolidation rate of dredge sludge, it is found that if the total height of the treated dredged sludge is 9.0 m and the 5.0 m high yard is designed with double-layer PHDs, the optimal PHDs laying ratios is 20%, the optimal location of the 2nd layer PHDs is at half of the total height of dredged sludge and the optimal stacking time is 140 days. [ABSTRACT FROM AUTHOR]

A traditional dredging systems on grab dredgers are typically controlled manually, which leads to low controlprecision and poor dredging flatness. Relying on a control modification project for a specific grab dredger, the operationalcharacteristics of the grab dredger and the driving characteristics of the hydraulic system were analyzed. Adepth -keepingalgorithm based on model predictive control and a fine dredging control algorithm based on fuzzy control were proposed. Adepth-keeping and fine dredging control system based on Siemens PLC was designed, ultimately achieving fully automatic"one -touch fine dredging". Practical application on the dredger demonstrates that the fully automatic operation process ofdepth-keeping and fine dredging control system is stable and reliable, with high control accuracy and flat excavation surfaces,which meets the construction operational requirements and enhances the construction efficiency of grab dredger operations. [ABSTRACT FROM AUTHOR]

The dredged soil encountered in dredging projects has become more and more complex, especially the SPT blowcounts of hard clay encountered in the construction of the deep water channel with trailing suction hopper dredger reaches 20,which is obviously different from the hard state of clay in previous channel dredging projects. In order to study the excavationmechanism of draghead tooth in hard clay, underwater fast cutting experiments were conducted on hard clay with SPT blowcounts of 18, 21, and 25 under different cutting speeds and depths to investigate the variation of draghead tooth cuttingresistance. By arranging the cutting resistance sensor on the draghead tooth, the underwater cutting resistance of the dragheadtooth under different cutting conditions was obtained, and the influence of cutting speed, cutting depth and SPT blow counts ofclay on the draghead tooth cutting resistance was analyzed respectively, which provides theoretical support for the design of thehard clay draghead. [ABSTRACT FROM AUTHOR]

Sparse borehole data and unreasonable sampling strategies pose challenges in accurately constructing geological profiles, resulting in inaccurate soil distribution information and impacting the design of implementation plans for dredging engineering. Therefore, an automatic construction and uncertainty analysis approach to the geological profile of dredging engineering is proposed using multiple-point geostatistics. The approach uses a training image instead of the variogram function, considering the spatial variability of the soil and adapting to learn high-order spatial information. This enables the characterization of spatial relationships and distribution patterns between multiple points. Subsequently, statistical uncertainty analysis is conducted based on the results obtained from stochastic simulations. The effects of neighboring cell numbers, threshold, and borehole spacings on the performance of our approach are systematically investigated and the optimal simulation parameters are determined. Additionally, the simulated geological profiles are categorized into three areas (high, medium, and low) based on the level of uncertainty, quantifying the uncertainty of the proposed approach. The equidistant method is then used for comparison and verification. When applied to a dredging engineering case in the Lianyungang Channel, the approach achieved a prediction accuracy of over 93.7% and successfully quantified boundary areas with high uncertainty in soil layers. This shows the enhanced capacity of the approach to capture characteristics of soil distribution. The approach reduces the area of high uncertainty by 11.4%, demonstrating advancements in selecting drilling locations. The study will provide decision support for geological surveys in dredging engineering and provide reliable soil information for subsequent construction. [ABSTRACT FROM AUTHOR]

In response to the long-term non-degradation and environmental pollution caused by the use of horizontal plastic drainage boards, a new approach is proposed in this study, which involves employing horizontal straw drainage system under vacuum preloading treatment for dredging sludge. Through laboratory model tests, the results show that horizontal straw drainage system exhibited excellent performance in treating dredged sludge, with an optimal spacing design of 40–60 cm. During the vacuum preloading test, the straw drainage system continuously degraded, and the degradation by-products of straw, in turn, enriched elements like nitrogen, phosphorus, potassium, etc., in the soil. The two processes of the degradation of straw drainage system and the eco-reinforcement of dredged sludge interacted actively with each other. Finally, a new reinforcement method for on-site dredging sludge was proposed by installing layered straw drainage boards. Therefore, straw drainage system was highly recommended for field application, due to their cost-effective and environmentally friendly characteristics. [ABSTRACT FROM AUTHOR]

This paper proposes an efficient productivity-aware optimization framework that utilizes hybrid machine learning with parallel global search to timely and appropriately adjust the critical control parameters (CCPs) of a cutter suction dredger (CSD) during construction. This optimization framework consists of three main parts. First, a hybrid Jaya–multilayer perceptron (MLP) algorithm was developed to rapidly construct a model that captures the interaction between construction parameters and slurry concentration. Next, the preliminary coarse results for the CCPs are determined through multi-parameter sensitivity analysis. Finally, the proposed resilient-zone parallel global search algorithm was employed to further optimize the CCPs, yielding more precise optimization results. To validate the proposed optimization framework and implement the in-situ service, it is applied to a real-world case study involving "Tianda" CSD construction. The results demonstrated that the average optimization duration is 6.7 s, which is shorter than the data acquisition interval of 8 s. Our approach improves the computational efficiency by 9.4 times compared with traditional optimization control methods. Additionally, there is a significant increase in the slurry concentration, with the maximum growth rate reaching 81.64%. [ABSTRACT FROM AUTHOR]

Regarding the issue of the first domestic double trunnions cutter suction dredger "TianKun" not being able toindependently complete the entire process of switching the upper and lower trunnions on the construction location, the two keycomponents of the upper and lower suction pipelines and maintenance platform that affect on-site switching have been retrofitdesigned to improve the speed and convenience of the whole process of ladder position switching. Aretrofit design scheme wasproposed based on the original ship structure, which uses the rotation of the ladder to drive specialized diagonal short pipes torealize pipeline connection below the waterline, and uses hydraulic cylinders to drive the overall lifting of the maintenanceplatform to realize the location matching between the maintenance platform and the ladder, and the effectiveness and reliabilityof the redesigned components are analyzed and verified through indoor model tests and finite element simulations. The resultsshow that the redesigned pipeline device can effectively center and seal, the redesigned maintenance platform structure isreasonable, and the strength and stiffness meet the requirements for use, which provides an effective solution for theimprovement of double trunnions cutter suction dredgers such as "TianKun", and can also provide a reference for future newship design. [ABSTRACT FROM AUTHOR]

Submarine pipeline route detection is of great significance for waterway dredging construction, while the traditionaldetection techniques have many problems, such as single technical means, low efficiency, unable to determine the buriedsection information and so on. In order to improve the accuracy of submarine pipeline detection results and operationalefficiency, relying on Ningbo -Zhoushan port Tiaozhoumen waterway expansion project, comprehensively uses the side -scansonar, sub-bottom profiler and marine magnetic detection technology to detect the submarine pipeline in the engineering area.The side-scan sonar results are used as the base data support of the submarine pipeline in the exposed section, and the subbottom profiler buried depth results and the magnetic detection inversion buried depth results confirm each other, which jointlyimproves the accuracy of submarine pipeline discrimination. The engineering application results show that the joint applicationof the three detection techniques in submarine pipeline detection is reliable, with significantly improved detection accuracy andoperational efficiency, and good applicability. It has a good reference and promotion role in similar projects. [ABSTRACT FROM AUTHOR]

The USACE boasts a navigation portfolio of over 19,312 km (12,000 mi) of shallow draft [from 2.74 m (9 ft) to 4.27 m (14 ft)] inland and intracoastal waterways, 20,921 km (13,000 mi) of deep draft [4.27 m (14 ft) and greater] channels, and 400 ports, harbors, and turning basins. To ensure that these channels remain navigable and at congressionally authorized dimensions, channel maintenance practices are performed annually by dredging. Most of these dredging operations are performed by private companies under contract to the USACE districts. With an abundance of navigation channel maintenance needs and a limited dredging fleet, accurate scheduling and the timely arrival of the dredging fleet is required. Project delays due to production issues, weather delays, contracting issues, or both will generally impact future scheduled projects, navigation, and commerce. Nonawardable bids happen when the contractor(s) proposal(s) are too high compared with the Independent Government Estimate (IGE). These nonawardable bids lead to significant time delays, because the USACE district must then engage in bid verification calls, negotiations, the potential cancellation of the contract solicitation, or both and the subsequent resolicitation for work. Therefore, it is extremely important that USACE cost estimates adequately reflect the level of effort the project requires when capturing all project-associated costs. This paper aims to summarize the USACE conceptual approach to dredge cost estimating by highlighting the complex variables that are associated with this type of estimate. [ABSTRACT FROM AUTHOR]

With the continuous development of dredging engineering and dredging business, the requirements for monitoring the dredging construction process are also increasing. Aiming at the problems of poor display effect and low accuracy in 3D visualization monitoring during the dredging process of existing dredgers, a universal 3D visualization system for dredger construction operations was designed and developed based on the Unity3D engine. The system realizes the 3D visualization display of key dredging equipment driving, underwater terrain generation and rendering, and real-time terrain reconstruction. Through actual dredger application verification, the system can effectively improve construction efficiency and quality, enhance construction accuracy, reduce the occurrence of missed excavation and over excavation, and has important engineering application value. [ABSTRACT FROM AUTHOR]

In the dredging of the Yellow River, a common practice involves extracting alluvial fill from the river and depositing it on the rear side of the embankment, serving the dual purpose of river dredging and reinforcing the embankment. Nevertheless, there are few studies on the consolidation of alluvial fill extracted from the Yellow River. In this paper, laboratory experiments were conducted to examine the change in hydraulic conductivity during the consolidation process of the alluvial fill. Besides, a numerical model was established to investigate the dissipation law of excess pore water pressure and the settlement law of layered consolidation of alluvial fill. According to the research, the main conclusions can be drawn as follows: (1) During the consolidation process of the alluvial fill, the hydraulic conductivity exhibited a linear decline as the consolidation pressure increased. (2) The consolidation speed under the variable hydraulic conductivity case is lower than that on the condition when the hydraulic conductivity is constant. (3) In layered construction, the consolidation rate of alluvial fill decelerates with the augmentation of layers. Additionally, the dissipation rate of pore water pressure at the top of the alluvial fill surpasses that at the bottom. (4) Setting a geotextile mat can accelerate the consolidation speed and shorten the consolidation time of alluvial fill by 8.3%–30%. [ABSTRACT FROM AUTHOR]

Copyright of Sociologia Italiana is the property of EGEA S.p.A and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study is based on a natural experiment carried out in the Biebrza National Park, Poland. The study site was a channel inhabited by Anodonta anatina, A. cygnea, Unio pictorum and U. tumidus. The deepening of the channel to restore ecosystem connectivity provided an opportunity to conduct this study. Mussels were collected before dredging, held in captivity for 48 h, measured, individually tagged and released post-dredging to the same 5-m channel sections they originated from. They were subsequently monitored for three consecutive years. Mussel survival remained high throughout the study, and no increased mortality in the year following reintroduction was observed. There was no growth retardation. Mussel mobility was low, with most individuals remaining in the same channel section in which they were released. Recolonisation patterns were consistent with the composition of mussel communities in adjacent unaffected habitats. Although dredging drastically changes mussel habitat, some characteristics: microclimate, water chemistry, nutrient availability and host fish can remain adequate. Our study shows that reintroducing mussels to the same site can serve as an effective mitigation conservation measure and can be preferable to translocation, particularly when carried out under time pressure with limited possibilities of assigning appropriate destination sites. [ABSTRACT FROM AUTHOR]

GCTS hollow cylinder apparatus was used to perform a series of tests on dredger fill from Tianjin under different initial stress states. This cyclic loading mode can simulate the rotation of the principal stress direction induced by wave loading. The effects of the initial intermediate principal stress parameter, initial shear stress and initial orientation angle of principal stress on softening index of dredger fill were investigated. A stiffness softening model which can consider different initial stress states was established. The test results show that when two of the three initial stress parameters remain unchanged, the softening index decreased with the increase of any other parameter. Among them, the initial orientation angle of principal stress has a great influence on stiffness softening. Based on the regression analysis of the test data, the relationship between the generalized shear strain ratio and the number of cycles under different cyclic shear stress amplitudes is proposed. Subsequently, the dynamic strength characteristics of the dredger fill were studied. It is found that the dynamic strength decreased significantly with the increasing initial angle of the principal stress, which can be accurately described by the model proposed in this article. [ABSTRACT FROM AUTHOR]

Copyright of Stratum Plus Journal is the property of P.P. Stratum plus and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Deep learning methods paired with sidescan sonar (SSS) are commonly used in underwater search-and-rescue operations for drowning victims, wrecks, and airplanes. However, these techniques are primarily used to detect mine-like objects and are rarely applied to identifying features in dynamic dredge pit environments. In this study, we present a Sandy Point dredge pit (SPDP) dataset, in which high-resolution SSS data were collected from the west flank of the Mississippi bird-foot delta on the Louisiana inner shelf. This dataset contains a total of 385 SSS images. We then introduce a new Effective Geomorphology Classification model (EGC). Through ablation studies, we analyze the utility of transfer learning on different model architectures and the impact of data augmentations on model performance. This EGC model makes geomorphic feature identification in dredge pit environments, which requires extensive experience and professional knowledge, a quick and efficient task. The combination of SSS images and the EGC model is a cost-effective and valuable toolkit for hazard monitoring in marine dredge pit environments. The SPDP SSS image dataset, especially the feature of pit walls without a rotational slump, is also valuable for other machine learning models. [ABSTRACT FROM AUTHOR]

The port of Tanger Med stands as the first port in Africa and the Mediterranean, with a throughput capacity of up to 9 million TEUs annually, accommodating the globe's largest vessels, such as ULCVs and MGX-24 classes, which boast capacities nearing 24,000 TEUs. To advance the safety and efficiency of handling deep-drafted vessels, the Tanger Med Port Authority, in cooperation with other terminals partners, try to deploy a sophisticated IoT-based system. This system integrates a high-precision non-linear 3D sea-keeping engine with detailed metocean forecasts, encompassing data on waves, winds, and other hydrodynamic factors. This IoT solution has been instrumental as a decision-support tool, facilitating the Harbormaster and Pilot teams in safely managing vessel transits. It has enabled an increase in the maximum allowable draft to 17.4 meters without requiring dredging. This paper delves into a model validation study assessing the effectiveness of the IoT solution in enhancing dynamic under-keel clearance management at Port Tanger Med, underlining its crucial role in improving operational efficiencies and ensuring navigational safety. [ABSTRACT FROM AUTHOR]

In the current implementation process for dredging projects, due to the lack of an accurate understanding of underwater soil characteristics, construction teams often find it difficult to accurately understand the soil condition. Not only does this lead to a reduced dredger operation efficiency, but it may also cause delays to the project's progress, as well as increasing its cost. Therefore, there is an urgent need to closely integrate soil analysis technology with dredging construction to ensure that projects can be completed efficiently and to a high standard. Therefore, this paper proposes a soil modeling and prediction method based on a three-dimensional point cloud model. The research objective is to propose a new method of soil mass identification with a strong generalization ability and function, which can not only be applied to dredging engineering but can also identify and analyze statistics of land soil and its mass. The accuracy of this method, based on a convergent grid, can reach 95%. [ABSTRACT FROM AUTHOR]

Santos is the most important Brazilian port, handling about 162 million of tons in 2022. In 2010, there was a great capital dredging to deepen the Access Channel to 15 m deep (Chart Datum - CD). This depth was not achieved, due to inefficiency on dredging procedures. Previous studies have indicated that, in order to maintain the bathymetric condition presented by the survey carried out in March 2016, an annual dredging of approximately 4,325,000 m³ would be necessary. This value increases for different project depths, increasing by 15%, 55%, and 80%, considering drafts of 15, 16, and 17 meters, respectively. Considering this situation, this study evaluated the possibility of implementing jetties in the region of the Port of Santos, using a calibrated hydrodynamic and morphological computational model for the area of interest. From the simulation of two different scenarios to represent local hydrodynamic conditions, reductions of approximately 45%, 40%, 35%, and 30% were estimated for the condition presented by the 2016 bathymetry and for draft depths of 15, 16, and 17 meters, respectively. [ABSTRACT FROM AUTHOR]

There is a consensus on the need to reduce the emissions of carbon compounds. The increase in global greenhouse gas (GHG) emissions in the maritime industry poses a serious challenge to environmental sustainability, climate change, and the operating costs of ships. This article shows how hybrid versus diesel propulsion technology for ships can help reduce carbon dioxide (CO2) emissions and fuel consumption, and how these changes can be achieved. The need to reduce exhaust emissions and the increasing need for the shipping industry to seek alternative fuels means that existing regulations for marine engines and engine emissions are being updated almost constantly and new regulations are being formulated. The cost implications of the new regulations may lead to an increase in emissions as engines with lower fuel consumption are chosen, i.e., larger marine engines. Alternative approaches are needed to reduce CO2 emissions and fuel consumption, which could ultimately lead to hybrid propulsion for ships. This paper examines the current state of greenhouse gas emissions in shipping by analyzing the CO2 emissions and operating costs of two ships of the same type with similar technical and technological characteristics and different propulsion systems to gain insight into the problem. This paper compares the reductions in CO2 emissions, fuel consumption, and fuel costs for two suction hopper dredgers with standard diesel and hybrid propulsion. The technical characteristics, CO2 emissions, fuel consumption, and price of the two ships were analyzed to determine the advantages and disadvantages of each propulsion system. The novelty of this study is that two suction hopper dredgers from the same company with similar technical–technological characteristics but different propulsion systems were used for the case study and a mathematical procedure for calculating CO2 and other greenhouse gasses was presented in comparison, all to determine to what extent and in what way the hybrid propulsion system of a ship can contribute to reductions in CO2 emissions and fuel costs at the ship and company levels compared to a standard diesel propulsion system. This comparative analysis shows how much lower CO2 emissions, fuel consumption, and fuel cost savings can be expected when using a hybrid propulsion system compared to a standard diesel propulsion system. Finally, a conclusion is drawn on the efficiency and environmental compatibility of the two systems. [ABSTRACT FROM AUTHOR]

Introduction: Dredging operation is happening at an increased rate due to the impetus gained towards inland navigation and land reclamation. The spud system is an integral component of a Cutter suction dredger (CSD) which anchors the hull at the dredging location. The spud embedded in the soil maintains the position of the dredger and offers resistance to the motion of the CSD. Methods: In this present study, the spud is modelled as an Euler–Bernoulli beam using finite element analysis. The resistance offered by the soil is evaluated experimentally. Soil stiffness is modelled using two spring elements which restrain the motion of the spud in the transverse and rotational directions. The spud system is subjected to external force due to wave loading. The wave load is determined along the length of the spud using the Morison equation. Heave and pitch are the degrees of freedom of the dredge hull which are restrained by the spud. The ship's rigid body dynamics are identified using the experimental study. The identified dredge hull is coupled to the spud. The numerical model of the spud system is subjected to random wave loading. A case study is carried out using Monte-Carlo simulation by varying the soil stiffness. The maximum response of the system is evaluated at the top of the spud. A metamodel for the system is developed based on the maximum response at spud and soil stiffness using the Gaussian process emulator (GPE). Results: The theoretical responses of the system due to theoretical and experimental wave loading conditions show similar characteristics. During the validation study, it is observed that the metamodel is predicting the soil stiffness accurately. Conclusion: The predictive analysis of the soil-spud system provides a good indication of the embedment of the spud. The analysis indicates that the condition monitoring of the embedment of the spud can be assessed by the metamodel developed using GPE. [ABSTRACT FROM AUTHOR]

Electrical tomography sensors have been widely used for pipeline parameter detection and estimation. Before they can be used in formal applications, the sensors must be calibrated using enough labeled data. However, due to the high complexity of actual measuring environments, the calibrated sensors are inaccurate since the labeling data may be uncertain, inconsistent, incomplete, or even invalid. Alternatively, it is always possible to obtain partial data with accurate labels, which can form mandatory constraints to correct errors in other labeling data. In this paper, a semi-supervised fuzzy clustering algorithm is proposed, and the fuzzy membership degree in the algorithm leads to a set of mandatory constraints to correct these inaccurate labels. Experiments in a dredger validate the proposed algorithm in terms of its accuracy and stability. This new fuzzy clustering algorithm can generally decrease the error of labeling data in any sensor calibration process. [ABSTRACT FROM AUTHOR]

The mud pump water sealing system (MPWSS) is important in the efficient operation and prolonged service life of the cutter suction dredger's (CSD) mud pump. Considering that the underwater pump operates underwater and the shaft seal water pressure sensor is prone to failure, a hybrid deep learning model MCNN transformer is proposed to predict the underwater pump shaft seal water pressure in the event of sensor failure. This paper uses big data from the dredging project to deeply excavate the relationship between the shaft end sealing water pressure and other construction data by combining experience and artificial intelligence, and then uses multi-scale convolutional neural network (MCNN) to reconstruct the data, highlighting the time series characteristics of the multi-scale data were then input into the transformer model for prediction, and compared with a single MCNN, transformer model and four other neural networks. Finally, the cutter suction dredger "Hua An Long" was selected as an application research case; experimental comparisons were conducted on seven different models to verify the accuracy and applicability of the MCNN-transformer model. [ABSTRACT FROM AUTHOR]

Global scallop fisheries are economically important but are associated with environmental impacts to seabed communities resulting from the direct physical contact of the fishing gear with the seabed. Gear modifications attempting to reduce this contact must be economically feasible such that the catch numbers for the target species is maintained or increased. This study investigated the outcome of reducing seabed contact on retained catch of scallops and bycatch by the addition of skids to the bottom of the collecting bag of scallop dredges. We used a paired control experimental design to investigate the impact of the gear modification in different habitat types. The modified skid dredge generally caught more marketable scallops per unit area fished compared with the standard dredge (+5%). However, the skid dredge also retained more bycatch (+11%) and more undersize scallops (+16%). The performance of the two dredges was habitat specific which indicates the importance of adjusting management measures in relation to habitat type. To realize the potential environmental benefits associated with the improvement in catchability of this gear modification, further gear modification is required to reduce the catch of undersize scallops and bycatch. Furthermore we advocate that technical gear innovations in scallop dredging need to be part of a comprehensive and effective fisheries management system. [ABSTRACT FROM AUTHOR]

Eutrophication of freshwater ecosystems is a global problem, but restoration can be difficult due to ongoing problems relating to water pollution, sedimentary nutrient stores and altered aquatic biodiversity. Mitigation of Eutrophication is often conducted alongside transplantation of submerged macrophytes and dredging, but knowledge of ecosystem response to post‐dredging transplantation of submerged macrophytes is limited.We report a long‐term (2008–2018) in situ monitoring study to evaluate the effects of different restoration measures: dredging only (Dredged) and dredged with post‐transplantation of submerged macrophytes (Dredged with macrophytes) conducted in five subtropical eutrophic lakes, Taihu basin. Water and sediment nutrients, bloom‐forming algae Microcystis and macroinvertebrate were monitored every 2 years for each treatment and compared with reference areas (Control) established in unrestored parts of the same lake.Dredging only decreased sediment nutrients (e.g. carbon, phosphorus) significantly; however, this effect diminished about 5 years later. Dredged with macrophytes had a stronger, longer lasting positive effect on water quality than dredged alone. Disturbance caused by dredging (without macrophytes transplantation) decreased the biomass of Microcystis, while transplantation of macrophytes shortly after dredging did not contribute to the decreasing of Microcystis biomass. The biomass of Microcystis in Dredged with macrophytes areas was always similar to Control over the period of our monitoring.A positive effect of submerged macrophytes transplantation post‐dredging was found for macroinvertebrate abundance and diversity: Dredged with macrophytes areas had significantly higher macroinvertebrate biomass and richness than Dredged areas after 9 years' recovery. Macroinvertebrate richness in Dredged with macrophytes areas nearly doubled compared to Control, while Dredged areas were just restored to Control levels.Synthesis and applications: Our study provides an long‐term field monitoring with new findings about the benefits and caution of submerged macrophytes transplantation post‐dredging and the effect of partial restoration, which could inform eutrophic waterbody restoration schemes. [ABSTRACT FROM AUTHOR]

To investigate the settlement behaviour under alternate vacuum preloading, a series of laboratory tests considering different influencing factors, such as vacuum pressure and alternating criterion, were conducted. Based on experimental data, a new settlement prediction model, which can synthetically reflect the effects of vacuum pressure, alternating criterion, and improvement time, was proposed. The prediction model took into account the influence of improvement depth and variations in vacuum pressure. The model was validated using several case studies and laboratory tests. Comparisons between the proposed model and layer-wise summation method results indicate that the calculated results of the proposed model are closer to the actual settlement with errors consistently less than 10%. The proposed model can conveniently and accurately predict the ultimate settlement of high water content dredger fill improved by vacuum preloading method. [ABSTRACT FROM AUTHOR]

Vacuum is an important parameter in cutter suction dredging operations because the equipment is underwater and can easily fail. It is necessary to analyze other parameters related to the vacuum to make real-time predictions about it, which can improve the construction efficiency of the dredger under abnormal working conditions. In this paper, a data-driven method for predicting the vacuum of the underwater pump of the cutter suction dredger (CSD) is proposed with the help of big data, machine learning, data mining, and other technologies, and based on the historical data of "Hua An Long" CSD. The method eliminates anomalous data, standardizes the data set, and then relies on theory and engineering experience to achieve feature extraction using the Spearman correlation coefficient. Then, six machine learning methods were employed in this study to train and predict the data set, namely, lasso regression (lasso), elastic network (Enet), gradient boosting decision tree (including traditional GBDT, extreme gradient boosting (XGBoost), light gradient boosting machine (LightGBM)), and stacking. The comparison of the indicators obtained through multiple rounds of feature number iteration shows that the LightGBM model has high prediction accuracy, a good running time, and a generalization ability. Therefore, the methodological framework proposed in this paper can help to improve the efficiency of underwater pumps and issue timely warnings in abnormal working conditions. [ABSTRACT FROM AUTHOR]

Large, low-lying rivers have a variety of societal uses and show a wide range of disturbances. One such example, the Apalachicola River in the Florida Panhandle, experienced anthropogenic activities that altered its hydrologic, geomorphic, and ecologic condition. The river's sand bars enlarged more than threefold in area because of dredge disposal and localized incision from anthropogenic activities during a navigation project. Once dredging ended, the river experienced passive recovery through the slow regrowth of riparian vegetation, with sand bars reducing in area ~18% from 2005 to 2015. The outcomes of tree-line change analyses from 1999 to 2019 indicate a higher recovery rate in the first decade (1999-2010), migrating fastest in locations where vegetation islands stabilize sediments. To help accelerate vegetation regrowth, during the growing seasons of 2018 and 2019, we planted willow stakes at various positions and microhabitats covering ~3.6 ha of three enlarged sand bars near Blountstown, FL. Our mapping shows some synergies between passive recovery and active restoration as tree-line expansion had the fastest rates between 2019 and 2021. Our study gives insights and guidance into passive recovery and restoration projects involving plantings on large, low-lying rivers. [ABSTRACT FROM AUTHOR]

In major harbors and ports in the United States and its territories, the US Army Corps of Engineers maintains federal navigation channels in proximity to coral reefs (e.g., Honolulu Harbor, HI; Miami Harbor, FL; Apra Harbor, Guam) and other sensitive habitats. To effectively predict potential adverse impacts from dredging activities near these sensitive habitats, a holistic approach to improve understanding of the pressures on these habitats is needed to foster a more complete prediction of risk drivers. To achieve this, risk‐based frameworks that account for the full range of natural and anthropogenic impacts need to be adapted and applied specifically for assessing and managing indirect dredging impacts on sensitive environments. In this article, we address this need by incorporating a drivers–pressures–stressors–condition–response (DPSCR4) conceptual framework to broaden a comprehensive conceptual model of the coupled human–ecological system. To help understand these complex interactions, DPSCR4 was applied to evaluate dredging and other unrelated environmental pressures (e.g., terrestrial runoff) in a proof‐of‐concept dredging project in Honolulu Harbor, Hawai'i, USA, with a focus on the indirect effects of dredge plumes. Particle tracking models and risk‐based tools were used to evaluate sediment resuspended during a hypothetical mechanical dredging activity near sensitive coral habitats. Stoplight indicators were developed to predict indirect sediment plume impacts on coral and then compared to exposure modeling results. The strengths and limitations of the approach are presented and the incorporation of the risk framework into environmental management decisions is discussed. Integr Environ Assess Manag 2024;20:547–561. Published 2023. This article is a U.S. Government work and is in the public domain in the USA. Key Points: A holistic risk‐based approach is needed to ascertain risks from dredging placement activities and other stressors to sensitive habitats such as coral reefs.An approach based on a drivers–pressures–stressors–condition–response (DPSCR4) framework was used to improve our understanding of the complex interactions among the multiple stressors impacting the ecosystem.A proof‐of‐concept dredging project in Honolulu Harbor, Hawai'i, USA, is presented that combines particle tracking models and existing risk‐based tools to evaluate sediment resuspended during a hypothetical mechanical dredging activity near sensitive coral reefs.This risk approach provides a means for assessing and managing environmental risks from a holistic perspective while providing opportunities to inform the management of sensitive habitats. [ABSTRACT FROM AUTHOR]

Dredging hoses are flexible and are particularly suitable for slurry transportations for mud or sand in dredging projects. To achieve sufficient bending stiffness and to prevent the pipe body from collapsing, this type of hose segment is a composite structure that is embedded with several cord reinforcement layers and steel wires in its rubber layer. To quickly evaluate the nonlinear bending mechanical properties of rubber hoses, this study proposes the equivalent stiffness method of linear superposition, which is verified by test data and numerical results. The results show that the equivalent bending stiffness method proposed in this study is in good agreement with numerical and experimental results. Then, by comparing the calculation results of the hose string, it was demonstrated that the linear stiffness superposition method proposed in this study can also accurately predict the bending mechanical behavior characteristics of string hose, and provide reliable guidance for hose design in practice. [ABSTRACT FROM AUTHOR]

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At present, the grab dredgers mostly rely on manual experience to control the closure of the grab during construction. In the process of closure, the projection of the bucket tooth trajectory in the vertical plane is a curve, which leads to low control accuracy and uneven operation area of the grab. Based on Newton iteration method, the control equation for the horizontal excavation motion of the grab is solved, and an automatic program is designed to control the rotation speed of the grab lifting winch and opening and closing winch, so that the projection of the bucket tooth motion trajectory in the vertical plane is a straight line, and the working area formed after excavation is a plane. The simulation results show that this method can effectively improve the excavation accuracy of grab and save the amount of dredging work. The research results can improve the operation ability of grab dredger and have important engineering application value. [ABSTRACT FROM AUTHOR]

Dredging is a common technique for managing eutrophication problems in waters, reducing the accumulation of pollutants by removing sediments from the bottom of water bodies. However, dredging can have complex impacts on lake ecosystems, and it is crucial to understand its benefits and mechanisms for the environment. In this paper, the dredged and undredged areas in the Caohai portion of Dianchi Lake were studied to analyze the effects of dredging on nitrogen–phosphorus transport and conversion and changes in nitrogen–phosphorus morphology content and its mechanisms by comparing the nitrogen–phosphorus morphology content and percentage, the nitrogen–phosphorus ratio, and the release contribution of the two areas. It was found that the ratio of stabilized nitrogen (SN) to stabilized phosphorus (SP) in the dredged area was lower than that in the undredged area and the BD-P and TOC content had a large turnaround at the 16–20 cm position of the sediment in the dredged area. The main conclusions were that the dredging would disrupt the internal equilibrium of the lake system for many years, with the greatest effect on the balance of the BD-P in the phosphorus forms of the sediment, and that the column cores of the dredged area at 0 to 16 cm might be newly accumulated sediments after the dredging project. However, with time, the distribution of nitrogen and phosphorus forms in the newly accumulated sediments will gradually reach a new equilibrium. In addition, dredging will also cause significant changes in the retention efficiency of nitrogen and phosphorus in the sediment, and the stable nitrogen and phosphorus forms will be released and transformed into unstable nitrogen and phosphorus forms. [ABSTRACT FROM AUTHOR]

Trailing suction hopper dredger is a kind of hydraulic dredger, it has the characteristics of self-propelled, selfloading, self-dredging, self-unloading, it is the main force in dredging and blowing works, it is widely used in the world, it can be said that where there is a big dredging project where there is a trailing suction hopper dredger's figure. The loading optimization process of trailing suction hopper dredger contains a lot of dredging parameters related to soil type, and the soil type under different working conditions is not very clear. In this study, we present a hybrid optimization technique based on simulated annealing and multi-population genetic algorithm to enhance the loading efficiency of a trailing suction hopper dredger and to examine the variation of dredged soil parameters. The soil parameters of the spoil hopper deposition model were estimated using this hybrid optimization algorithm. The experimental results show that the soil parameters are successfully estimated and verified by our measured construction data of a trailing suction hopper dredger. In addition, our proposed method has the highest accuracy of soil parameter estimation, the fastest algorithm convergence, and excellent robustness compared to the other three intelligent optimization methods. In addition, our method successfully avoids the phenomenon of premature convergence that usually occurs in traditional genetic algorithms, and the parameters show strong adaptability to different vessels under the same dredging area. [ABSTRACT FROM AUTHOR]